Alternately, your adversary sponsors AdWords ads against your site on the first page of some popular search engine. The ad may be somewhat like this: Be Careful Of This Fraud (keyword). This is sufficient to annul years of hard work put in by you to bring your business to its present level.
Taking steps to maintain and further boost your reputation as an honest businessman in such circumstances is called online reputation management.
One way to persuade your competitor is to request him politely to remove the offending comments and then threaten him with legal action if he still persists. If this tactic also fails, it would be better to fight him out at his own ground, that is, by playing the SEO game with him.
You can try to push the page/site with offensive comments to the second results page of search engine, for example, Google. This can be achieved through several steps;
1. Push other sites that have lower rank than your competitor’s site above it on the Google research page. Assuming the site with the negative comments against you ranks fourth on Google page, you should try to boost the rank of the sites below it to supersede it to a higher rank.
You can do so by applying SEO techniques. You can, for example, add favorable comments on this site. Book mark it in as many social media sites such as Technocrati, Digg, Delicious etc as possible. You may even write positive reviews about it on the home page of your site by placing links at suitable places.
2. Ask someone you know who commands authority for his site to write a good review for your site and publish the same on your home page saying: What others are saying about us.
3. Create new content and syndicate it through articles, blogs, newsletters, etc for seoing your own site. You may also submit the content for syndication through RSS feeds. In this way you can indirectly persuade the audience to ignore the comments against your site.
4. Create new sub-domains or sister domains of your site. Google often considers the sub-domains as different sites, but they command the same authority as the primary domain. Post preferably new content on the sub-domain site. You need not fill it with hundreds of pages. Just 10-12 pages should suffice.
Reputation management basically involves delivering (sometimes over-delivering) what you promise in terms of quality and quantity. Once this trust is built up, it is difficult for your adversaries to shake it.